Wealth Building
Financial Independence -- Calculate Your Number
Work becomes optional when your investments generate more than you spend. Here's the math and the path.
The Speedrun Take
Financial independence means your investment portfolio generates enough passive income to cover your expenses forever. The math is simpler than most people think: multiply your annual expenses by 25. That's your FI number. A $50,000/year lifestyle needs $1.25M invested. A $30,000/year lifestyle needs $750,000. Your savings rate determines how fast you get there.
The 4% Rule -- What It Is
The 4% rule comes from the Trinity Study (1994), which analyzed 30-year retirement periods using historical market data. The finding: a 4% annual withdrawal rate survived 95%+ of all historical scenarios, including the Great Depression and the 1970s stagflation.
How it works: withdraw 4% of your portfolio in year one, then adjust that dollar amount for inflation each year. Over 30 years, your portfolio is very unlikely to run out.
The FI Number Formula
Annual Expenses x 25
Because 1 / 25 = 4%. Your FI number is simply 25 times what you spend per year.
Important Caveat
The 4% rule was designed for 30-year retirements. If you retire at 35, you may need a 3-3.5% withdrawal rate (30-33x expenses) to cover 50+ years.
FI Number by Expense Level
Find your annual expenses and read across. Use 30x if you plan to retire before 50.
| Annual Expenses | FI Number (25x) | Early Retire (30x) |
|---|---|---|
| $25,000 | $625,000 | $750,000 |
| $40,000 | $1,000,000 | $1,200,000 |
| $60,000 | $1,500,000 | $1,800,000 |
| $80,000 | $2,000,000 | $2,400,000 |
| $100,000 | $2,500,000 | $3,000,000 |
Worth noting
$40,000/year in expenses is very achievable for people who own their home, have no debt, and live reasonably. That's not extreme frugality -- that's a solid middle-class life with no mortgage payment.
FI Number Calculator
Expected Annual Return: 7%
Your Results
Your FI Number (4% rule / 25x)
$1,250,000
Conservative FI (3.5% withdrawal / 29x)
$1,450,000
Years to FI (at 7% return)
26 yrs 8 mo
CoastFI Number
$164,209
Amount needed today that grows to your FI number by age 65 with no more contributions (assuming you're 35 today -- adjust mentally)
$50,000 of $1,250,000 needed
How Savings Rate Affects Your Timeline
| Savings Rate | Monthly Savings | Years to FI |
|---|---|---|
| 10%(you) | $463/mo | ~40 years |
| 20% | $1,042/mo | ~33 years |
| 30% | $1,786/mo | ~26 years |
| 40% | $2,778/mo | ~20 years |
| 50% | $4,167/mo | ~16 years |
| 60% | $6,250/mo | ~12 years |
Based on your annual expenses of $50,000. Monthly savings column shows what each savings rate implies for your expense level.
The Types of FIRE
FIRE is not one-size-fits-all. Different versions suit different spending levels and lifestyles.
| Type | Lifestyle |
|---|---|
| LeanFIRE | Very frugal, often LCOL area |
| FIRE | Comfortable middle-class |
| FatFIRE | Comfortable or luxurious |
| BaristaFIRE | Semi-retired, part-time covers some expenses |
| CoastFIRE | Stop contributing, let compounding do the work |
CoastFIRE Explained
At CoastFIRE, you have enough invested that if you never contribute another dollar, your portfolio will compound to your full FI number by traditional retirement age (65). You only need to earn enough to cover your current expenses -- no more saving required.
Example: $200,000 invested at age 35, growing at 7%/year = $1,540,000 by age 65 -- enough for FI at $60,000/year in expenses.
The Savings Rate Is Everything
Years to financial independence from zero, assuming 7% real return and 4% withdrawal rate.
| Savings Rate | Years to FI |
|---|---|
| 10% | 51 years |
| 20% | 37 years |
| 30% | 28 years |
| 40% | 22 years |
| 50% | 17 years |
| 60% | 12.5 years |
| 70% | 8.5 years |
Key insight
Doubling your savings rate doesn't halve the time to FI -- it reduces it by 50-70%. Why? Because you're both saving more and needing less. Lower expenses mean a smaller FI number, which accelerates the timeline from both directions simultaneously.
Source: Mr. Money Mustache savings rate chart / foundational FIRE math
The Investment Strategy for FIRE
Accumulation Phase (Building to FI)
- -Aggressive allocation: 80-100% stocks (FZROX + FZILX or VTI + VXUS)
- -Max all tax-advantaged accounts first: 401(k) to HSA to Roth IRA to taxable brokerage
- -Taxable brokerage for overflow -- tax-efficient funds only
Withdrawal Phase (After FI)
- -Rule of 72(t) for early access to tax-advantaged accounts if needed
- -Roth conversion ladder for early retirees
- -Keep 1-2 years of expenses in cash or bonds to avoid selling stocks in a down market (sequence of returns risk)
Start the accumulation phase
Fidelity offers 0.00% expense ratio index funds (FZROX) — a solid home for Roth IRA, 401(k) rollovers, and taxable brokerage overflow.
The "One More Year" Syndrome
One of the most common FIRE traps: you hit your number, but you keep working "just one more year" to be safe. Then another. Then another.
At some point you have more than enough. The risk of running out of money is real -- but so is the cost of your time. Working an extra five years at a job you'd leave costs you five years you cannot get back. The math should give you confidence to act, not just more reasons to delay.
Getting Started -- 3 Steps
Calculate your annual expenses
Track your spending for 3 months if you're unsure. Add it up and multiply by 4. That's your annual run rate.
Multiply by 25
That's your FI number. Write it down. Every dollar you invest closes the gap.
Follow the investment order
401(k) match first, then HSA, then Roth IRA, then more 401(k), then taxable brokerage. Every account filled gets you closer to FI.
Related Guides
Start Investing
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No account minimum, 0.00% expense ratio on FZROX, and the best Roth IRA setup available. Open your account in 10 minutes and put your first dollar toward your FI number.